A conventional variable displacement swash plate type compressor (hereinafter referred to as compressor) is disclosed in Japanese Patent Laid-Open No. 5-172052. In the compressor, a housing is formed by a front housing, a cylinder block, and a rear housing. A suction chamber and a discharge chamber are formed in the front housing and the rear housing, respectively. Further, a pressure regulation chamber is formed in the rear housing.
A swash plate chamber and a plurality of cylinder bores are formed in the cylinder block. Each of the cylinder bores is configured by a first cylinder bore formed on the rear side of the cylinder block, and a second cylinder bore formed on the front side of the cylinder block. Each of the first cylinder bores and the second cylinder bores has the same diameter.
A drive shaft is inserted in the housing and is supported rotatably in the cylinder block. A swash plate, which can be rotated by rotation of the drive shaft, is provided in the swash plate chamber. A link mechanism, which allows the inclination angle of the swash plate to be changed, is provided between the drive shaft and the swash plate. Here, the inclination angle means an angle formed by the swash plate with respect to the direction perpendicular to the rotational axis of the drive shaft.
Further, a piston is accommodated so as to be able to reciprocate in each of the cylinder bores. Specifically, each of the pistons includes a first head section reciprocating in each of the first cylinder bores, and a second head section reciprocating in each of the second cylinder bores. Since each of the first cylinder bores and the second cylinder bores of the cylinder bores has the same diameter, each of the first head sections and the second head sections of the pistons also have the same diameter. Thereby, in this compressor, first compression chambers are formed by each of the first cylinder bores and each of the first head sections, and second compression chambers are formed by each of the second cylinder bores and each of the second head sections. A conversion mechanism is configured such that, by rotation of the swash plate, each of the pistons is reciprocated in each of the cylinder bores at a stroke corresponding to the inclination angle of the swash plate. Further, the inclination angle can be changed by an actuator, and a control mechanism is configured to control the actuator.
In the swash plate chamber, the actuator is arranged on the side of the first cylinder bores with respect to the swash plate. The actuator includes an actuator main body and a control pressure chamber. The actuator main body includes a non-rotating movable body, a movable body, and a thrust bearing. The non-rotating movable body is arranged in the control pressure chamber so as not to be rotatable integrally with the drive shaft and covers a rear end portion of the drive shaft. The inner peripheral surface of the non-rotating movable body is configured to rotatably slidably support the rear end portion of the drive shaft, and is configured to be able to move in the direction of the rotational axis. Further, the outer peripheral surface of the non-rotating movable body is configured to slide in the direction of the rotational axis in the control pressure chamber, and is configured not to slide around the rotational axis. The movable body is connected to the swash plate so as to be movable in the direction of the rotational axis. The thrust bearing is provided between the non-rotating movable body and the movable body.
The control pressure chamber is provided on the rear side of the cylinder block, that is, on the side of the first cylinder bores in the cylinder block. A pressing spring, which urges the non-rotating movable body toward the front side, is provided in the control pressure chamber. Further, a pressure control valve, which changes the pressure in the control pressure chamber so as to enable the non-rotating movable body and the movable body to move in the direction of the rotational axis, is provided between the pressure regulation chamber and a discharge chamber.
The link mechanism is arranged so that, according to a change of the inclination angle of the swash plate, the top dead center position of the second head section of each of the pistons is moved more than the top dead center position of the first head section of each of the pistons. The link mechanism includes a movable body and a lug arm fixed to the drive shaft. A long hole, which extends in the direction perpendicular to the rotational axis and in the direction approaching the rotational axis from the outer peripheral side, is formed at the rear end portion of the lug arm. The swash plate is supported pivotably around a first pivotal axis by a pin inserted into the long hole on the front side of the swash plate. Further, a long hole, which extends in the direction perpendicular to the rotational axis and in the direction approaching the rotational axis from the outer peripheral side, is also formed at the front end portion of the movable body. The swash plate is supported pivotably around a second pivotal axis in parallel with the first pivotal axis by a pin inserted into the long hole at the rear end of the swash plate.
In this compressor, when the pressure regulation valve is controlled to be opened so that the discharge chamber communicates with the pressure regulation chamber, the pressure in the control pressure chamber is made higher than the pressure in the swash plate chamber. Thereby, the non-rotating movable body and the movable body are moved toward the front side. By this movement, the inclination angle of the swash plate is increased, so that the strokes of the pistons are increased. Thereby, the compression capacity per one revolution of the compressor is increased. When the pressure regulation valve is controlled to be closed so that the discharge chamber does not communicate with the pressure regulation chamber, the pressure in the control pressure chamber is reduced to almost the same pressure as that in the swash plate chamber. Thereby, the non-rotating movable body and the movable body are moved toward the rear side. By this movement, the inclination angle of the swash plate is reduced, so that the strokes of the pistons are reduced. As a result, the compression capacity per one revolution of the compressor is reduced.
Here, in each of the pistons of this compressor, the top dead center position of the second head section of the piston is moved more largely than the top dead center position of the first head section of the piston. Therefore, when the inclination angle of the swash plate is made close to 0 degree, a slight amount of compression work is performed only in the first compression chambers, and no compression work is performed in the second compression chambers.
Meanwhile, in a compressor, high controllability is required in order that the compression capacity can be rapidly increased or reduced according to an operation condition of a vehicle, or the like, to which the compressor is mounted. To cope with this requirement, also in the above-described conventional compressor, it is considered to increase the size of the control pressure chamber of the actuator. Therefore, it is considered that, in the compressor, the inclination angle of the swash plate is rapidly changed by sliding the non-rotating movable body and the movable body in the direction of the rotational axis with a large thrust force.
However, in this compressor, the control pressure chamber is formed in the cylinder block. Therefore, when the size of the control pressure chamber is increased, the size of the cylinder block is increased, so that the entire size of the compressor is increased. As a result, the mounting performance of the compressor to a vehicle, or the like, is lowered.
In this compressor, when the diameter of the cylinder bores is reduced to increase the size of the control pressure chamber of the actuator, desired compression capacity cannot be secured.
The present invention has been made in view of the above described circumstances. An object of the present invention is to provide a variable displacement swash plate type compressor which has high controllability and which can exhibit high mounting performance and secure sufficient compression capacity.